The following description of background art may include insights, discoveries, understandings or disclosures, or associations together with disclosures not known to the relevant art prior to the present invention but provided by the invention. Some such contributions of the invention may be specifically pointed out below, whereas other such contributions of the invention will be apparent from their context.
Nowadays, hoisting devices or cranes are widely applied in mechanical, chemical, manufacturing, process, construction and extractive industries, as well as in shipyards or ports and terminals all over the world. An overhead crane, also known as a bridge crane, is a type of crane where the hook-and-line mechanism runs along a horizontal beam that itself runs along two widely separated rails. The hook-and-line mechanism may contain a trolley to move along the horizontal beam, and a hoist arranged to the trolley to lift the items. Often the overhead crane is in a long factory building and runs along rails along the building's two long walls. It is similar to a gantry crane. Overhead cranes typically consist of either a single beam or a double beam construction. These may be built using typical steel beams or a more complex box girder type. Most hoists use some sort of pulley system; pulleys are wheels that are specially designed to guide a rope, cable, belt, or chain, and they are usually mounted on an axle to allow the wheel to spin freely. These pulleys can be mounted to a motor that spins the unit to control the feed of cable. The hoist may be an electric hoist, such as an electric chain hoist, an electric wire rope hoist and an electric belt hoist, using an electric motor as a lifting motor. The hoist equipment may include any of the controls for a motorized pulley unit, the motor electric motor itself, and the pulley housing mounted on the trolley. The controls may include various electric circuitries, such an inverter for controlling the operation of the host, such as speed and direction on the lifting, enabling soft starts and reducing stress forces affecting the crane and the structures.
A good condition of hoisting devices, such as bridge cranes and gantry cranes, is desirable in terms of both economic and security aspects. A fault of a hoisting device e.g. a fault in its brake, may lead to dropping of the load, which may cause damage to the hoisting device and/or danger to personnel working near the hoisting device. During maintenance, the hoisting device is not in productive use. From an economic point of view, the downtime of expensive machinery like the hoisting device should be kept as short and few as possible.
Maintenance of hoisting devices requires highly trained personnel, who may be servicing hoisting devices on a wide geographical area. Since there is only a limited number of capable maintenance personnel, there may be some delay involved between a detection of a maintenance need of a hoisting device, e.g. in case of a fault, and arrival of the maintenance personnel to servicing the hoisting device.
A maintenance plan of a hoisting device includes pre-scheduled maintenances specifying operations to be performed during maintenance. The maintenance plan tries to minimize faults of the hoisting device between the scheduled maintenances and thereby minimizing the downtime.
However, there may still be faults that occur between the scheduled maintenances, therefore requiring more visits by the maintenance personnel and decreasing the uptime of the hoisting device. These faults may be by nature such that they are difficult to detect by the maintenance personnel during the scheduled maintenances. The difficulty may follow from detection of the possible faults requiring a disproportional amount of time to be found, if there is any to be found. Accordingly, the extra time spent during maintenance for detecting faults may have a poor efficiency compared to the cost of the downtime of the hoisting device. The difficulty of detection of the faults may also follow from the faults being impossible to be detected by human eye or by conventional maintenance equipment carried by the maintenance personnel visiting the hoisting device.
An ongoing challenge in crane manufacturing and usage is how to keep crane operation safe during a longer service period with limited maintenance budgets.